CB[8]-based rotaxane as a useful platform for sensitive detection and discrimination of explosives

Based on a naphthalene-threaded cucurbit[8]uril (CB[8]) rotaxane structure on a solid substrate, a new strategy for rapid, fully reversible, and highly sensitive detection of a broad class of explosives was developed by using one receptor. Due to the unique confinement effect and size exclusion of the CB[8] cavity, it is found that the intercalation of an explosive compound in the constructed rotaxane can significantly influence the photophysical property of the naphthalene core in the confined nanocavity of CB[8]. Dependent on the electronic structures and the sizes of explosive compounds, the fluorescence of the naphthalene core would be quenched or enhanced to different extents, leading to the direct detection and discrimination of distinctively different groups of trace explosives in the vapor phase, especially including the challenging aliphatic nitro-organics (RDX, HMX and PETN). Control experiments were performed to show the different sensing behaviors between the common organic vapors and nitrate-based explosives, which made it easy to realize the discrimination between target analytes and interferents. Due to the surface-attached sensing elements, a rapid response was also achieved in this system. Moreover, the non-covalent nature of the resulting heteroternary complex indicates that the trapped target molecules in the rotaxane structure are facilely removable by simply washing, demonstrating an excellent regeneration of the constructed explosive sensors for real-world application. The performed experiments suggested that the rotaxane structure-based sensing protocol opened a new way to develop a new kind of explosive sensors enabling a richer identification of threats.